What is the climate in the Pacific Ocean? Climate zones of the oceans Winter in the South Pacific

Deviations in the location and local differences within them are caused by the characteristics of the underlying surface (warm and cold currents) and the degree of influence of the adjacent continents with the circulation developing above them.

The main features over the Pacific Ocean are defined by five areas of high and low pressure. In the subtropical latitudes of both hemispheres over the Pacific Ocean, two dynamic high-pressure areas are constant - the North Pacific, or Hawaiian, and South Pacific maxima, the centers of which are located in the eastern part of the ocean. In equatorial latitudes, these regions are separated by a constant dynamic region of low pressure, which is more strongly developed in the west. To the north and south of the subtropical maxima at higher latitudes there are two minima - the Aleutian with a center over the Aleutian Islands and , elongated from east to west, in the Antarctic zone. The first exists only in winter in the Northern Hemisphere, the second - throughout the year.

Subtropical maxima determine the existence of a stable system of trade winds in the tropical and subtropical latitudes of the Pacific Ocean, which consists of a northeast trade wind in the Northern Hemisphere and a southeast trade wind in the Southern Hemisphere. The trade wind zones are separated by an equatorial calm zone, in which weak and unstable winds predominate with a high frequency of calms.

The Northwest Pacific is a pronounced monsoon region. In winter, the northwest monsoon dominates here, bringing cold and dry air from the Asian mainland, in summer - the southeast monsoon, carrying warm and humid air from the ocean. Monsoons disrupt the trade wind circulation and lead to the flow of air from the Northern Hemisphere to the Southern Hemisphere in winter, and in the opposite direction in summer.

Permanent winds are strongest in temperate latitudes and especially in the Southern Hemisphere. The frequency of storms in the Northern Hemisphere in temperate latitudes ranges from 5% in summer to 30% in winter. In tropical latitudes, constant winds reach storm strength extremely rarely, but sometimes tropical winds pass here. Most often they occur in the warm half of the year in the Western Pacific. In the Northern Hemisphere, typhoons are directed mainly from the area lying to the east and northwest, to, in the Southern - from the region of the islands of New Hebrides and Samoa to. In the eastern part of the ocean, typhoons are rare and occur only in the Northern Hemisphere.

The distribution of air is subject to the general latitudinal. The average temperature in February decreases from + 26 -I- 28 "C in the equatorial zone to - 20 ° C in the strait. The average August temperature varies from + 26 - + 28 °C in the equatorial zone to + 5 °C in the strait.

The pattern of temperature decrease from to high latitudes in the Northern Hemisphere is disturbed under the influence of warm and cold currents and winds. In this regard, there are large differences between the temperature in the east and west at the same latitudes. With the exception of the region adjacent to Asia (mainly the region of the marginal seas), in almost the entire zone of the tropics and subtropics, that is, within the greater part of the ocean, the west is several degrees warmer than the east. This difference is due to the fact that in this belt the western part of the Pacific Ocean is warmed by the trade wind currents (and East Australian) and theirs, while the eastern part is cooled by the California and Peruvian currents. In the Northern Hemisphere, on the contrary, the west is colder than the east in all seasons. The difference reaches 10-12 ° and is mainly due to the fact that here the western part of the Pacific Ocean is cooled by the cold one, and the eastern part is heated by the warm Alaska current. In temperate and high latitudes of the Southern Hemisphere, under the influence of westerly winds and the predominance of winds with a westerly component in all seasons, temperature changes occur naturally and there is no significant difference between east and west.

And precipitation during the year is greatest in areas with lowered and near mountain coasts, since in both areas there is a significant rise in air currents. In temperate latitudes, cloudiness is 70-90, in the equatorial zone 60-70%, in trade wind zones and in subtropical areas of high pressure it decreases to 30-50, and in some areas in the Southern Hemisphere - up to 10%.

The largest falls in the trade winds meeting zone, which lies north of the equator (between 2-4 and 9 ~ 18 ° N), where intense upward currents of moisture-rich air develop. In this zone, the amount of precipitation is more than 3000 mm. In temperate latitudes, the amount of precipitation increases from 1000 mm in the west to 2000-3000 mm or more in the east.

The smallest amount of precipitation falls on the eastern outskirts of the subtropical high pressure areas, where the prevailing downward air currents and cold ones are unfavorable for moisture condensation. In these areas, the amount of precipitation is: in the Northern Hemisphere west of the California Peninsula - less than 200, in the Southern Hemisphere west of - less than 100, and at some points even less than 30 mm. In the western parts of the subtropical regions, the amount of precipitation increases to 1500-2000 mm. In the high latitudes of both hemispheres, due to weak evaporation at low temperatures, the amount of precipitation decreases to 500-300 mm or less.

In the Pacific Ocean, fogs form mainly in temperate latitudes. They are most frequent in the area adjacent to the Kuril and Aleutian, in the summer season, when the water is colder than the air. The frequency here is 30-40% in summer, 5-10% or less in winter. In the Southern Hemisphere in temperate latitudes, the frequency of fogs during the year is 5-10%.

Date of: 01.04.2017

Climatic conditions

Temperatures
- The average air temperature over the Pacific Ocean in winter is from + 26 ° C at the equator to - 20 ° C over the Bering Strait; in summer according to +8 ° С... +27 ° С
- The average water temperature in the Pacific Ocean is 2 ° C higher than in the Indian and Atlantic, which is explained by the placement of most of the ocean in a hot thermal zone;
- A smaller part is located in the temperate and subarctic climatic zones;

Precipitation
- The average amount of precipitation at the equator is 3000 mm, in temperate zones - from 1000 mm in the west to 2000-3000 mm in the east;

atmospheric circulation
- Atmospheric pressure areas affecting atmospheric circulation: Aleutian Low; North Pacific, South Pacific, Antarctic highs;
- Atmospheric circulation: trade winds (tropical, subtropical latitudes), which causes typhoons; western (temperate latitudes), in temperate latitudes in the northeast, pronounced monsoon circulation.

Properties of water masses

All types of water masses are represented in the Pacific Ocean.
So, according to latitude, equatorial, tropical, temperate and polar regions are distinguished.
By depth - near-bottom, deep, intermediate and surface.
The main properties of water masses are their temperature and salinity.

So, the average water temperature on the surface in February is + 26 ° ... + 28 ° С near the equator and -0.5 ° ... - 1 ° С near the Kuriles; in August, the water temperature is 25 ° ... + 29 ° С near the equator and + 5 ° ... +8 ° С - in the Bering Strait.

The highest salinity of waters is in subtropical latitudes (35.5-36.5%o), and in temperate latitudes it decreases (33.5-30%o).

Ice forms in the north and south of the ocean, on most of the coast of Antarctica. In winter, icebergs reach 61°-64°S. sh., in summer - up to 46 ° -48 ° S. sh.

ocean currents

The circulation of the atmosphere forms a powerful circulation of surface currents in the Pacific Ocean. So, in the tropical latitudes of the Northern Hemisphere. And under the influence of an area of ​​constant high atmospheric pressure over Hawaii, water masses (like air masses) move clockwise, bringing warm water from the equator. In the Southern Hemisphere, on the contrary, the circulation of air and water occurs counterclockwise due to the area of ​​​​constant high atmospheric pressure in the east of the tropical belt. The circulation of air and water masses in the Southern Hemisphere causes different water temperatures in the east and west of the ocean.

The Pacific Ocean has the largest number of surface currents.

Warm: Kuroshio, North Pacific, Alaska, South Equatorial, North Equatorial, East Australian.

Cold; Peruvian, Californian, Kuril, Western winds.

The Atlantic and Pacific, Indian and Arctic Oceans, as well as continental waters, make up the World Ocean. The hydrosphere plays an important role in shaping the planet's climate. Under the influence of solar energy, part of the water of the oceans evaporates and falls as precipitation on the territory of the continents. Surface water circulation humidifies the continental climate, bringing heat or cold to the mainland. The water of the oceans changes its temperature more slowly, therefore it differs from the temperature regime of the earth. It should be noted that the climatic zones of the oceans are the same as on land.

Climate zones of the Atlantic Ocean

The Atlantic Ocean has a large length and four atmospheric centers are formed in it with different air masses - warm and cold. The temperature regime of water is affected by water exchange with the Mediterranean Sea, the Antarctic seas and the Arctic Ocean. All the climatic zones of the planet pass in the Atlantic Ocean, therefore, in different parts of the ocean there are completely different weather conditions.

Climatic zones of the Indian Ocean

The Indian Ocean is located in four climatic zones. In the northern part of the ocean, the monsoon climate, which was formed under the influence of the continental. The warm tropical zone has a high temperature of the air masses. Sometimes there are storms with strong winds, and even tropical hurricanes occur. The greatest amount of precipitation falls in the equatorial zone. It gets cloudy here, especially in the area close to Antarctic waters. Clear and favorable weather occurs in the region of the Arabian Sea.

Climate zones of the Pacific Ocean

The climate of the Pacific Ocean is influenced by the weather of the Asian continent. Solar energy is distributed zonal. The ocean is located in almost all climatic zones, except for the Arctic. Depending on the belt, in different areas there is a difference in atmospheric pressure, and different air currents circulate. In winter, strong winds prevail, and in summer - southerly and weak ones. Calm weather almost always prevails in the equatorial zone. Warmer temperatures in the western Pacific, cooler in the east.

Climatic zones of the Arctic Ocean

The climate of this ocean was influenced by its polar location on the planet. Persistent ice masses make weather conditions harsh. In winter, there is no solar energy and the water is not heated. In summer, there is a long polar day and a sufficient amount of solar radiation enters. Different parts of the ocean receive different amounts of precipitation. The climate is influenced by water exchange with neighboring water areas, Atlantic and Pacific air currents.

Over the Pacific Ocean, they are formed under the influence of planetary factors, covering most of them. As well as over the Atlantic, in the subtropical latitudes of both hemispheres above the ocean there are centers of constant baric maxima, in equatorial latitudes there is an equatorial depression, in temperate and polar regions - areas of low pressure: in the north - seasonal (winter) Aleutian minimum, in the south - part of the permanent Antarctic (more precisely, the Antarctic) belt. The formation of the climate is also influenced by baric centers formed over the adjacent continents.

Wind systems are formed in accordance with the distribution of atmospheric pressure over the ocean. Subtropical maxima and equatorial depression determine the effect of trade winds in tropical latitudes. Due to the fact that the centers of the North Pacific and South Pacific maxima are shifted towards the American continents, the highest speeds and stability of the trade winds are observed precisely in the eastern part of the Pacific Ocean.

Southeast winds stay here up to 80% of the time in the annual withdrawal, their prevailing speeds are 6-15 m/s (maximum - up to 20 m/s). Northeast winds are somewhat less stable - up to 60-70%, their prevailing speeds - 6-10 m/s. The trade winds rarely reach storm strength.

The maximum wind speeds (up to 50 m/s) are associated with the passage of tropical cyclones - typhoons.

The frequency of occurrence of tropical cyclones in the Pacific Ocean (according to L. S. Minina and N. A. Bezrukov, 1984)

Typically, typhoons occur in the summer and originate in several areas. The first region is located east of the Philippine Islands, from where tropical cyclones move northwest and northward towards East Asia and further northeast towards the Bering Sea. Every year, hitting the Philippines, Japan, Taiwan, the east coast of China and some other areas, typhoons, accompanied by heavy rains, hurricane winds and storm waves up to 10-12 m high, cause significant damage and lead to the death of thousands of people. Another area is located northeast of Australia in the area of ​​the New Hebrides, from here typhoons move towards Australia and New Zealand. Tropical cyclones are rare in the eastern part of the ocean; their origin is in the coastal regions adjacent to Central America. The paths of these hurricanes run through the coastal regions of California towards the Gulf of Alaska.

In the near-equatorial latitudes in the trade wind convergence zone, weak and unstable winds prevail, and calm weather is very characteristic. In the temperate latitudes of both hemispheres, westerly winds prevail, especially in the southern part of the ocean. It is in the middle latitudes of the Southern Hemisphere that they have the greatest strength (“roaring forties”) and constancy. Frequent cyclones on the polar front determine here the formation of storm winds with a speed of more than 16 m/s and a frequency of up to 40% in the autumn-winter period. Directly off the coast of Antarctica, easterly winds prevail at high latitudes. In the temperate latitudes of the Northern Hemisphere, strong westerly winds during the winter period give way to weak ones in summer.

The northwestern part of the Pacific Ocean is an area of ​​pronounced monsoonal circulation. The extremely powerful Asian high in winter forms north and northwest winds here, carrying cold and dry air from the mainland. In summer, they are replaced by south and southeast winds that carry warm and humid from the ocean to the mainland.

Air temperatures and precipitation

The large length of the Pacific Ocean in the meridional direction determines significant interlatitudinal differences in thermal parameters near the water surface. The latitudinal zonality of heat distribution is clearly manifested over the ocean area.

The highest temperatures (up to 36-38°C) are observed in the region of the northern tropic to the east of the Philippine Sea and in the region of the California and Mexican coasts. The lowest - in Antarctica (up to - 60 ° C).

The distribution of air temperature over the ocean is significantly affected by the direction of the prevailing winds, as well as warm and cold ocean currents. In general, at low latitudes, the western Pacific is warmer than the eastern.

The influence of the land of the continents surrounding the ocean is extremely great. The predominantly latitudinal course of the isotherms of any month is usually disturbed in the zones of contact between the continents and the ocean, as well as under the influence of the prevailing air currents and ocean currents.

The influence is extremely important in the distribution of air temperature over the ocean. it is colder over the southern half of the ocean than over the northern. This is one of the manifestations of the polar asymmetry of the Earth.

The distribution of precipitation is also subject to the general latitudinal zonality.

The greatest amount of precipitation falls in the equatorial-tropical zone of trade winds convergence - up to 3000 mm per year or more. They are especially abundant in its western part - in the area of ​​the Sunda Islands, the Philippines and New Guinea, where powerful convection develops under conditions of unusually fragmented land. To the east of the Caroline Islands, the annual precipitation exceeds 4800 mm. In the equatorial "calm zone" precipitation is significantly less, and in the east, in equatorial latitudes, a relatively dry zone is noted (less than 500 mm and even 250 mm per year). In temperate latitudes, annual precipitation is significant and amounts to 1000 mm or more in the west and up to 2000-3000 mm or more in the east of the ocean. The smallest amount of precipitation falls in the areas of action of subtropical baric maxima, especially along their eastern periphery, where descending air currents are most stable. In addition, cold ocean currents (California and Peru) pass here, contributing to the development of inversion. Thus, to the west of the California Peninsula, less than 200 mm falls, and off the coast of Peru and northern Chile, less than 100 mm of precipitation per year, and in some areas above the Peruvian Current, 50-30 mm or less. In the high latitudes of both hemispheres, due to weak evaporation at low air temperatures, the amount of precipitation is small - up to 500-300 mm per year or less.

The distribution of precipitation in the intratropical convergence zone is generally uniform throughout the year. The same is observed in subtropical areas of high pressure. In the area of ​​action of the Aleutian baric minimum, they fall mainly in winter during the period of the greatest development of cyclonic activity. The winter maximum of precipitation is also characteristic of the temperate and subpolar latitudes of the South Pacific Ocean. In the monsoonal northwestern region, the maximum precipitation occurs in the summer.

Cloudiness over the Pacific Ocean in the annual output reaches its maximum values ​​in temperate latitudes. In the same place, fogs are most often formed, especially over the water area adjacent to the Kuril and Aleutian Islands, where their frequency in summer is 30-40%. In winter, the likelihood of fogs is sharply reduced. Fogs are not uncommon near the western coasts of the continents in tropical latitudes.

The Pacific Ocean is found in all climatic zones except the Arctic.

Physical and chemical properties of waters

The Pacific Ocean is considered the warmest of the oceans on Earth. Its average annual surface water is 19.1°С (1.8°С above temperature and 1.5°С - ). This is explained by the huge volume of the water basin - the heat accumulator, the large water area in the most heated equatorial-tropical regions (more than 50% of the total), and the isolation of the Pacific Ocean from the cold Arctic basin. The influence of Antarctica in the Pacific Ocean is also weaker compared to the Atlantic and Indian Oceans due to its vast area.

The temperature distribution of the surface waters of the Pacific Ocean is determined mainly by heat exchange with the atmosphere and circulation of water masses. In the open ocean, isotherms usually have a latitudinal course, with the exception of areas with meridional (or submeridional) water transport by currents. Particularly strong deviations from latitudinal zonality in the temperature distribution of the surface waters of the ocean are noted near the western and eastern coasts, where meridional (submeridional) flows close the main circuits of the Pacific Ocean water circulation.

In the equatorial-tropical latitudes, the highest seasonal and annual water temperatures are observed - 25-29°C, and their maximum values ​​(31-32°C) belong to the western regions of the equatorial latitudes. At low latitudes, the western part of the ocean is warmer than the eastern part by 2-5°C. In areas of the California and Peruvian currents, the temperature can be 12-15°C lower than in coastal waters located at the same latitudes in the western part of the ocean. In the temperate and subpolar waters of the Northern Hemisphere, the western sector of the ocean, on the contrary, is colder than the eastern one by 3-7°C throughout the year. In summer, the water temperature in the Bering Strait is 5-6°C. In winter, the zero isotherm passes through the middle part of the Bering Sea. The minimum temperature here is up to -1.7-1.8°C. In Antarctic waters, in areas of floating ice, the water temperature rarely rises to 2-3°C. In winter, negative temperatures are observed south of 60-62 ° S. sh. In the temperate and subpolar latitudes of the southern part of the ocean, the isotherms have a smooth sublatitudinal variation; there is no significant difference in water temperatures between the western and eastern parts of the ocean.

Salinity and density of waters

The distribution of salinity in the Pacific Ocean follows general patterns. In general, this indicator at all depths is lower than in others, which is explained by the size of the ocean and the significant remoteness of the central parts of the ocean from the arid regions of the continents. The water balance of the ocean is characterized by a significant excess of the amount of atmospheric precipitation together with river runoff over the amount of evaporation. In addition, in the Pacific Ocean, in contrast to the Atlantic and Indian, at intermediate depths there is no entry of especially saline waters of the Mediterranean and Red Sea types. The centers of formation of highly saline waters on the surface of the Pacific Ocean are the subtropical regions of both hemispheres, since evaporation here significantly exceeds the amount of precipitation.

Both highly saline zones (35.5% in the north and 36.5% in the south) are above 20° latitude in both hemispheres. North of 40° N. sh. salinity decreases especially rapidly. At the head of the Gulf of Alaska, it is 30-31% o. In the Southern Hemisphere, the decrease in salinity from the subtropics to the south slows down due to the influence of the current of the West Winds: up to 60 ° S. sh. it remains more than 34%o, and off the coast of Antarctica it decreases to 33%o. Water desalination is also observed in equatorial-tropical regions with a large amount of precipitation. Between the centers of salinization and freshening of waters, the distribution of salinity is strongly influenced by currents. Along the shores of the current, in the east of the ocean, desalinated waters are carried from high latitudes to lower latitudes, and in the west - saline waters in the opposite direction. So, on the maps of isohalines, the "tongues" of freshened waters that come with the California and Peru currents are clearly expressed.

The most general pattern of changes in the density of waters in the Pacific Ocean is an increase in its values ​​from the equatorial-tropical zones to high latitudes. Consequently, the decrease in temperature from the equator to the poles completely covers the decrease in salinity throughout the space from the tropics to high latitudes.

Ice formation in the Pacific Ocean occurs in the Antarctic regions, as well as in the Bering, Okhotsk and Japan Seas (partially in the Yellow Sea, bays of the eastern coast of Kamchatka and Hokkaido Island and in the Gulf of Alaska). The distribution of ice mass over the hemispheres is very uneven. Its main share falls on the Antarctic region. In the north of the ocean, the vast majority of floating ice that forms in winter melts by the end of summer. Fast ice does not reach a significant thickness during the winter and is also destroyed in the summer. In the northern part of the ocean, the maximum age of ice is 4-6 months. During this time, it reaches a thickness of 1-1.5 m. The southernmost limit of floating ice was noted off the coast of about. Hokkaido at 40°N sh., and off the eastern coast of the Gulf of Alaska - at 50 ° N. sh.

The average position of the ice distribution boundary passes over the continental slope. The southern deep part of the Bering Sea never freezes, although it is located much north of the freezing areas of the Sea of ​​Japan and the Sea of ​​Okhotsk. The removal of ice from the Arctic Ocean is practically absent. On the contrary, in summer part of the ice is carried out of the Bering Sea into the Chukchi Sea. In the north of the Gulf of Alaska, several coastal glaciers (Malaspina) are known, which produce small icebergs. Usually in the northern part of the ocean, ice is not a serious obstacle to ocean navigation. Only in some years, under the influence of winds and currents, ice "plugs" are created that close the navigable straits (Tatarsky, Laperouse, etc.).

In the southern part of the ocean, large masses of ice are present all year round, and all types of it extend far to the north. Even in summer, the edge of the floating ice keeps on average about 70 ° S. sh., and in some winters with especially severe conditions, ice extends to 56-60 ° S. sh.

The thickness of floating sea ice reaches 1.2-1.8 m by the end of winter. It does not have time to grow more, as it is carried by currents to the north into warmer waters and collapses. There are no multi-year pack ice in Antarctica. Powerful sheet glaciers of Antarctica give rise to numerous icebergs that reach 46-50 ° S. sh. They reach furthest north in the eastern Pacific Ocean, where individual icebergs have been encountered at almost 40°S. sh. The average size of Antarctic icebergs is 2-3 km long and 1-1.5 km wide. Record dimensions - 400 × 100 km. The height of the above-water part varies from 10-15 m to 60-100 m. The main areas of iceberg occurrence are the Ross and Amundsen seas with their large ice shelves.

The processes of ice formation and melting are an important factor in the hydrological regime of water masses in the high-latitude regions of the Pacific Ocean.

Water dynamics

The features of circulation over the water area and adjacent parts of the continents primarily determine the general scheme of surface currents in the Pacific Ocean. The same type and genetically related circulation systems are formed in the atmosphere and ocean.

As in the Atlantic, in the Pacific Ocean, the northern and southern subtropical anticyclonic circulations of currents and the cyclonic circulation in the northern temperate latitudes are formed. But unlike other oceans, there is a powerful stable Inter-trade countercurrent here, which forms with the Northern and Southern Trade-wind currents two narrow tropical circulations in equatorial latitudes: the northern one is cyclonic and the southern one is anticyclonic. Off the coast of Antarctica, under the influence of winds with an eastern component blowing from the mainland, the Antarctic Current is formed. It interacts with the course of the West Winds, and here another cyclonic circuit is formed, especially well expressed in the Ross Sea. Thus, in the Pacific Ocean, in comparison with other oceans, the dynamic system of surface waters is most pronounced. The zones of convergence and divergence of water masses are associated with the circulations.

Off the western coasts of North and South America in tropical latitudes, where the surge of surface waters by the California and Peruvian currents is enhanced by steady winds along the coast, upwelling is most pronounced.

An important role in the circulation of the waters of the Pacific Ocean belongs to the subsurface Cromwell, which is a powerful stream moving under the South Trade Wind Current at a depth of 50-100 m or more from west to east and compensating for the loss of water driven by the trade winds in the eastern part of the ocean.

The length of the current is about 7000 km, the width is about 300 km, the speed is from 1.8 to 3.5 km/h. The average speed of most of the main surface currents is 1-2 km / h, the Kuroshio and Peruvian currents are up to 3 km / h. The Northern and Southern Trade winds differ in the greatest water transfer - 90-100 million m 3 / s, Kuroshio transfers 40-60 million m 3 / s. m 3 / s (for comparison, the California Current - 10-12 million m 3 / s).

Tides in most of the Pacific Ocean are irregular semidiurnal. Tides of a regular semidiurnal character prevail in the southern part of the ocean. Small areas in the equatorial and northern parts of the water area have daily tides.

The height of tidal waves averages 1-2 m, in the bays of the Gulf of Alaska - 5-7 m, in the Cook Bay - up to 12 m. The highest tide height in the Pacific Ocean was noted in the Penzhina Bay (Sea of ​​​​Okhotsk) - more than 13 m.

The highest wind waves (up to 34 m) are formed in the Pacific Ocean. The most stormy are the zones of 40-50 ° N. sh. and 40-60°S sh., where the height of the waves with strong and prolonged winds reaches 15-20 m.

Storm activity is most intense in the area between Antarctica and New Zealand. In tropical latitudes, the prevailing excitement is due to the trade winds, it is quite stable in direction and wave height - up to 2-4 m. Despite the huge wind speed in typhoons, the wave height in them does not exceed 10-15 m (since the radius and duration of these tropical cyclones are small ).

The islands and coasts of Eurasia in the northern and northwestern parts of the ocean, as well as the coasts of South America, are often visited by tsunamis, which repeatedly caused heavy damage and loss of life here.

Physical geography of continents and oceans

OCEANS

PACIFIC OCEAN

Climate and hydrological conditions of the Pacific Ocean

Pacific Ocean extends between 60° north and south latitude. In the north, it is almost closed by the land of Eurasia and North America, separated from each other only by the shallow Bering Strait with the smallest width of 86 km, connecting the Bering Sea of ​​the Pacific Ocean with the Chukchi Sea, which is part of the Arctic Ocean.

Eurasia and North America extend south as far as the Tropic of the North in the form of vast massive landmasses, which are the centers of the formation of continental air, capable of influencing the climate and hydrological conditions of neighboring parts of the ocean. South of the Tropic of the North, the land acquires a fragmentary character; to the coast of Antarctica, its large land areas are only Australia in the southwest of the ocean and South America in the east, especially its extended part between the equator and 20 ° S. latitude. South of 40°S The Pacific Ocean, together with the Indian and Atlantic, merge into a single water surface, not interrupted by large areas of land, over which oceanic air of temperate latitudes is formed, and where Antarctic air masses freely penetrate.

The Pacific reaches greatest width(almost 20 thousand km) within the tropical equatorial space, i.e. in that part of it, where during the year the thermal energy of the sun is most intensively and regularly supplied. In this regard, the Pacific Ocean receives more solar heat during the year than other parts of the World Ocean. And since the distribution of heat in the atmosphere and on the water surface depends not only on the direct distribution of solar radiation, but also on air exchange between land and water surface and water exchange between different parts of the World Ocean, it is quite clear that the thermal equator over the Pacific Ocean is shifted to the north. hemisphere and runs approximately between 5 and 10 ° N, and the northern part of the Pacific Ocean is generally warmer than the southern.

Consider the main pressure systems, which determine the meteorological conditions (wind activity, precipitation, air temperature), as well as the hydrological regime of surface waters (systems of currents, temperature of surface and subsurface waters, salinity) of the Pacific Ocean during the year. First of all, this is the near-equatorial depression (calm zone), somewhat extended towards the northern hemisphere. This is especially pronounced in the summer of the northern hemisphere, when an extensive and deep baric depression with a center in the Indus River basin is established over the strongly heated Eurasia. In the direction of this depression, streams of humid unstable air rush from the subtropical high-pressure centers of both the northern and southern hemispheres. Most of the northern half of the Pacific Ocean at this time is occupied by the North Pacific High, along the southern and eastern periphery of which monsoons blow towards Eurasia. They are associated with heavy rainfall, the amount of which increases towards the south. The second monsoon flow moves from the southern hemisphere, from the side of the tropical high pressure zone. In the northwest, there is a weakened western transfer towards North America.

In the southern hemisphere, where it is winter at this time, strong westerly winds, carrying air from temperate latitudes, cover the waters of all three oceans south of the 40°S parallel. almost to the coast of Antarctica, where they are replaced by east and southeast winds blowing from the mainland. The western transfer operates in these latitudes of the southern hemisphere and in the summer, but with less force. Winter conditions in these latitudes are characterized by heavy precipitation, storm winds, and high waves. With a large number of icebergs and floating sea ice, travel in this part of the oceans is fraught with great dangers. It is not for nothing that navigators have long called these latitudes the “roaring forties”.

At the corresponding latitudes in the northern hemisphere, the western transport is also the dominant atmospheric process, but due to the fact that this part of the Pacific Ocean is closed by land from the north, west and east, in winter there is a slightly different meteorological situation than in the southern hemisphere. With the western transport, cold and dry continental air enters the ocean from the side of Eurasia. It is involved in the closed system of the Aleutian Low, which is formed over the northern part of the Pacific Ocean, is transformed and carried to the coast of North America by southwestern winds, leaving abundant precipitation in the coastal zone and on the slopes of the Cordilleras of Alaska and Canada.

Wind systems, water exchange, features of the topography of the ocean floor, the position of the continents and the outlines of their coasts affect the formation of the surface currents of the ocean, and they, in turn, determine many features of the hydrological regime. In the Pacific Ocean, with its vast dimensions, within the intratropical space, there is a powerful system of currents generated by the trade winds of the northern and southern hemispheres. In accordance with the direction of movement of the trade winds along the margins of the North Pacific and South Pacific Ocean maxima facing the equator, these currents move from east to west, reaching a width of more than 2000 km. The North Trade Wind flows from the shores of Central America to the Philippine Islands, where it divides into two branches. The southern part spreads over the interisland seas and partly feeds the surface inter-trade countercurrent that runs along the equator and to the north of it, advancing towards the Central American Isthmus. The northern, more powerful branch of the North Trade Wind Current goes to the island of Taiwan, and then enters the East China Sea, skirting the Japanese islands from the east, gives rise to a powerful system of warm currents in the northern part of the Pacific Ocean: this is the Kuroshio Current, or the Japanese Current, moving at a speed of 25 to 80 cm/s. Near the island of Kyushu, the Kuroshio forks, and one of the branches enters the Sea of ​​Japan under the name of the Tsushima Current, the other goes out into the ocean and follows the eastern coast of Japan, until at 40 ° N. latitude. it is not pushed to the east by the cold Kuril-Kamchatka countercurrent, or Oyashio. The continuation of Kuroshio to the east is called the Kuroshio Drift, and then the North Pacific Current, which is directed to the coast of North America at a speed of 25-50 cm / s. In the eastern part of the Pacific Ocean, north of the 40th parallel, the North Pacific Current branches into the warm Alaska Current, heading towards the shores of South Alaska, and the cold California Current. The latter, following along the shores of the mainland, flows south of the tropic into the North Equatorial Current, closing the northern circulation of the Pacific Ocean.

Most of the Pacific Ocean north of the equator is dominated by high surface water temperatures. This is facilitated by the large width of the ocean in the intertropical space, as well as the system of currents that carry the warm waters of the Northern Equatorial Current to the north along the coasts of Eurasia and neighboring islands.

North Equatorial Current all year round carries water with a temperature of 25 ... 29 ° C. The high temperature of surface waters (up to approximately 700 m depth) persists within Kuroshio to almost 40°N. (27 ... 28 °С in August and up to 20 °С in February), as well as within the North Pacific Current (18 ... 23 °С in August and 7 ... 16 °С in February). A significant cooling effect on the northeast of Eurasia up to the north of the Japanese islands is exerted by the cold Kamchatka-Kuril Current, which originates in the Bering Sea, which in winter is intensified by cold waters coming from the Sea of ​​Okhotsk. From year to year, its power varies greatly depending on the severity of winters in the Bering and Okhotsk Seas. The region of the Kuril Islands and the islands of Hokkaido is one of the few in the northern part of the Pacific Ocean where ice occurs in winter. At 40° N when meeting with the Kuroshio current, the Kuril current plunges to a depth and flows into the North Pacific. In general, the temperature of the waters of the northern part of the Pacific Ocean is higher than in the southern part at the same latitudes (5 ... 8 ° C in August in the Bering Strait). This is partly due to limited water exchange with the Arctic Ocean due to the threshold at the Bering Strait.

South Equatorial Current moves along the equator from the shores of South America to the west and even enters the northern hemisphere up to about 5 ° north latitude. In the area of ​​the Moluccas, it branches: the bulk of the water, together with the North Equatorial Current, enters the system of the Intertrade Countercurrent, and the other branch penetrates into the Coral Sea and, moving along the coast of Australia, forms a warm East Australian current, which flows into the current off the coast of Tasmania. Western winds. The temperature of surface waters in the South Equatorial Current is 22...28 °С, in the East Australian in winter from north to south it varies from 20 to 11 °С, in summer - from 26 to 15 °С.

Circumpolar Antarctic or West Wind Current, enters the Pacific Ocean south of Australia and New Zealand and moves in a sublatitudinal direction to the shores of South America, where its main branch deviates to the north and, passing along the coasts of Chile and Peru under the name of the Peruvian Current, turns west, merging into the South Trade Wind , and closes the South Pacific Gyre. The Peruvian current carries relatively cold waters and reduces the air temperature over the ocean and off the western coasts of South America almost to the equator to 15...20 °C.

In distribution salinity surface waters in the Pacific Ocean, there are certain patterns. With an average salinity for the ocean of 34.5-34.6% o, the maximum indicators (35.5 and 36.5% c) are observed in zones of intense trade wind circulation in the northern and southern hemispheres (respectively between 20 and 30 ° N and 10 and 20°S) This is due to a decrease in precipitation and an increase in evaporation compared with equatorial regions. Up to the fortieth latitudes of both hemispheres in the open part of the ocean, salinity is 34-35% o. The lowest salinity is in high latitudes and in the coastal regions of the northern part of the ocean (32-33% o). There it is associated with the melting of sea ice and icebergs and the desalination effect of river runoff, so there are significant seasonal fluctuations in salinity.

The size and configuration of the greatest of the Earth's oceans, the features of its connections with other parts of the World Ocean, as well as the size and configuration of the surrounding land areas and the associated directions of circulation processes in the atmosphere created a number of features Pacific Ocean: the average annual and seasonal temperatures of its surface waters are higher than in other oceans; the part of the ocean located in the northern hemisphere is generally much warmer than the southern, but in both hemispheres the western part is warmer and receives more precipitation than the eastern part.

The Pacific Ocean, to a greater extent than other parts of the World Ocean, is the scene of the birth of an atmospheric process known as tropical cyclones or hurricanes. These are vortices of small diameter (no more than 300-400 km) and high speed (30-50 km/h). They form within the tropical convergence zone of the trade winds, as a rule, during the summer and autumn of the northern hemisphere and move first in accordance with the direction of the prevailing winds, from west to east, and then along the continents to the north and south. For the formation and development of hurricanes, a vast expanse of water is required, heated from the surface to at least 26 ° C, and atmospheric energy, which would impart translational motion to the formed atmospheric cyclone. The features of the Pacific Ocean (its size, in particular, the width within the intratropical space, and the maximum surface water temperatures for the World Ocean) create conditions over its water area that contribute to the origin and development of tropical cyclones.

The passage of tropical cyclones is accompanied by catastrophic events: destructive winds, heavy seas on the high seas, heavy rainfall, flooding of the plains on adjacent land, floods and destruction, leading to severe disasters and loss of life. Moving along the coasts of the continents, the most powerful hurricanes go beyond the intratropical space, transforming into extratropical cyclones, sometimes reaching great strength.

The main area of ​​origin of tropical cyclones in the Pacific Ocean is south of the Tropic of the North, east of the Philippine Islands. Moving initially to the west and northwest, they reach the shores of Southeast China (in Asian countries, these eddies bear the Chinese name "typhoon") and move along the continent, deviating towards the Japanese and Kuril Islands.

The branches of these hurricanes, deviating to the west south of the tropic, penetrate into the interisland seas of the Sunda archipelago, into the northern part of the Indian Ocean and cause destruction in the lowlands of Indochina and Bengal. Hurricanes originating in the southern hemisphere north of the Southern Tropic move towards the coasts of Northwest Australia. There they carry the local name "BILLY-BILLY". Another center of origin of tropical hurricanes in the Pacific Ocean is located off the western coast of Central America, between the Tropic of the North and the equator. From there, hurricanes rush to the coastal islands and coasts of California.